The advantages of using females prior to sexual maturity at 3 years of age are 1) it avoids the need for suppression prior to ovarian stimulation since no endogenous cycles are present, and 2) it does not interfere with colony breeding which depends on older animals. Phase 1 used Human Follicle stimulating Hormone (hFSH) in early pubertal (20-26 mos) and late pubertal (30-34 mos) females. Within each age group different levels of stimulation were administered. Low dose animals received 5 IU human follicle stimulation hormone (hFSH) twice daily for up to 12 days depending on the estradiol response. High dose animals received 10 IU (hFSH) twice daily for 10 days. 150 IU hCG was then given and a laparoscopic oocyte retrieval was done the following morning. Stimulation with low dose (hFSH) in early puberty (n=5) or late puberty (n=5) induced low estradiol levels (<200 pg/ml) and about one mature oocyte per animal. High dose stimulation (early pub n=8); (late pub n=4) resulted in estradiol levels of greater than 1000 pg/ml and almost 4 mature oocytes per animals. In Phase II late pubertal monkeys (n=2) were stimulated with the published dose of 1 mg pFSH for 5 days but the ovaries were not stimulated (early December). Increasing the dose to twice daily injections of 1 mg for 5 days resulted in one animal with an E2 of 876 pg/ml and 3 animals less than 250 pg/ml. No oocytes were retrieved from the responding animal when laparoscoped 12 hours post 500 IU hCG probably due to an early ovulation. The three other animals yielded 6 germinal vesical stage oocytes. Recent efforts involved stimulation at the same dose for 6 days with retrieval at 11 hours post 500 IU hCG which again only yielded 4 GV oocytes from 2 animals perhaps due to missing early ovulation and the mature oocyte. In summary, thus far, pFSH ovarian stimulation appears to require a higher dosage than previously published. Also, we have yet to establish fertilization as verified by 2PN visualization but appear to be stimulating the ovaries.